What is flashing tape, and can you use it on a roof?
Short answer. Flashing tape is a self-adhesive waterproof membrane, usually butyl or rubberized asphalt with a foil or film face, made to seal joints around windows, doors and penetrations. On roofs it belongs under metal flashing and around skylight curbs and wall joints as a second layer of protection; as an exposed patch on top of shingles it is a short-lived emergency fix.
Types of flashing tape
- Butyl: stays flexible across a wide temperature range and holds up better in sun and heat than asphalt types.
- Rubberized asphalt: common and inexpensive, but it can soften in high heat, and some products are not compatible with certain plastics and sealants.
- Acrylic adhesive: bonds to many surfaces, including in cool weather.
- Foil-faced versions: reflect UV and last longer when left exposed.
Where it belongs on a roof
- Wrapping skylight curbs and other roof openings before the metal flashing goes on.
- Covering small gaps or seams in the decking before underlayment.
- Roof to wall joints, behind step flashing, as a backup layer.
In each case the tape is a hidden layer under shingles or metal. It is not the primary flashing.
Where it does not belong
- As an exposed patch over cracked shingles or a leaking boot. Georgia sun and heat break most tapes down within a season or two, and the adhesive often fails on granule-covered shingles.
- In place of step flashing or counterflashing at a wall or chimney.
- Across valleys, where a patch can dam water.
Buying it
Widths run from a couple of inches to a foot or more, and butyl and foil-faced tapes cost more than basic asphalt types. For temporary roof use, pick a product the maker rates for UV exposure and apply it to a clean, dry surface. See ice and water shield in Georgia and roof flashing explained.